This research program aims to determine what functional sets of neurons make up the sensorimotor cortex of the domestic cat, how the sets are interconnected to form "neuronal circuitry," what thalamic inputs end upon what sets, which sets send information to what subcortical sites, and how activity in these cerebral "neuronal circuits" generates the patterns of external, net vertical current flow and surface voltage changes characteristic of the tissue. Studies are made of the response properties of large numbers of individual neurons, observed through extracellular microelectrode recording, during maneuvers designed to characterize them functionally, and during each of eight different "spontaneous" and evoked potentials. Through the methods of population analysis, the "circuitry" of the tissue is determined and the characteristics of its operation during each of the "spontaneous" and evokedpotentials is analyzed. For each potential, the pattern of net vertical current flow is calculated, and the relationship of this pattern to that of neuronal activity that produced it is determined. From these studies, it is possible to determine whether sensorimotor cortex has only two preferred modes of operation, as now seems probable. To aid in attaining the above objectives, a fully automated research facility is used featuring a computer-controlled microdrive system. Neurons responsive to the hunting stimulus are automatically detected, isolated and identified, and a pre-defined dynamically altering experiment is then performed on each neuon. Appropriate stimuli are delivered under computer command, data are acquired by the computer and immediately analyzed.